1. Field of the Invention
The present invention relates to a light quantity adjusting device, a lens barrel and an image pickup apparatus.
2. Description of the Related Art
A lens barrel of an image pickup apparatus such as a video camera or a digital still camera is frequently provided with a light quantity adjusting device (a diaphragm device) which adjusts the size of a diaphragm aperture whose center is located on the optical axis of an image pickup optical system incorporated in the lens barrel.
If only a pair of diaphragm blades is used to provide a small aperture state, diffraction deterioration will occur. To prevent the diffraction deterioration, light quantity adjusting devices are provided that use the pair of diaphragm blades in combination with an ND (neutral density) filter blade adapted to reduce the quantity of transmitted light.
One of such light quantity adjusting devices is proposed in which a single actuator drives the pair of diaphragm blades and the ND filter blade. See Japanese Patent Laid-open No. Hei 8-6105.
In addition, another one is proposed in which two independent actuators drive the pair of diaphragm blades and the ND filter blade. See Japanese Patent Laid-open No. 2000-122109.